<!doctype html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <!-- 实现理想视口,让布局视口的大小(网页的宽度) == 视觉视口的大小(设备屏幕的宽度) -->
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <!-- 有利于SEO优化, 搜索引擎优化-->
    <meta name="description" content="当前网页内容的关键字">
    <title>移动端视口</title>
    <style>
      * {
        margin: 0;
        padding: 0;
      }
      #box {
        width: 100px;
        height: 100px;
        background-color: red;
      }
    </style>
  </head>
  <body>
    <div id="box">AAA</div>
  </body>
</html>
